It is estimated that the average life span of hominids on the Africansavanna between 4,000,000 and 200,000 years ago was 20 years. This means that the population would be completely renewed about five times per century. It is further estimated that the population of hominids in Africa fluctuated between 10,000 and 100,000 individuals, thus averaging about 50,000 individuals. Roughly multiplying 40,000 centuries by 50,000 to 500,000 individuals per century, yields a total of 2 billion to 20 billion hominids, or an average estimate of about 10 billion hominids that lived during that approximately 4,000,000 year time span.[1] Other estimates have ranged from 45 to 110 billion.[2][3]